Spherical Particles and Their Surface Properties. I. Interaction of Water with the Surface of Spherical Silica

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Abstract
Spherical particles of silica were prepared by passing fine silica material through the O2–H2 flame. Spherical particles obtained were amorphous, creviceless, and very large in size compared to those of the starting material which indicates that spheres are made by complete comelting of a large number of fine particles. Water adsorption measurements showed that the rate of rehydration of the dehydroxylated silica surface is very slow, especially at low water pressures, and that the spherical silica has a heterogeneous surface, this heterogeneity being enhanced when the sample is heated at elevated temperatures. The ratio of the number of water molecules adsorbed in the first physisorption layer to that of the underlying surface hydroxyls was found to be 1:1.